I have an American Waltham "Jewel" series 6/0 wristwatch with a broken upper balance pivot. The hole and cap jewels both in the plate and in the cock appear to be in good condition. I have about twenty five years experience in clock repair, but am fairly new to the watch repair game. (It is a whole new learning experience! )
I have a Peerless 8mm lathe, and I believe I can come up with the proper size collet (or use a shellac collet) to chuck up the staff, but is this too small to be learning on? Would I be better advised to send it out? I do not own a set of poising jaws, and wonder if that is likely to be a problem, even if I am able to successfully swap out the staff?

Sorry for the long post with all the questions, but I really do suspect that I may be getting in "over my head".

Hi,
Are you talking about making a new staff?
If you are looking for a replacement staff 6/0 size P/N 26106, I have some I can sell you.
mrmel.mrmel@gmail.com
Mel

I meant a replacement staff. But my concern is that I might mess up the balance arms trying to cut the old one off, and whether after replacing the wheel on the new staff, does it have to be poised?

David,

A 6S is a bit small for a first attempt at staff replacement, but since you have experience you can probably pull it off. Cut the old staff off at the hub side, not the rivet side. Take it down to where there is just a small sliver left and then use a staking set to tap it out in the direction of the rivet. This will prevent any damage to the arms and you will not distort the hole. Before staking the new staff onto the balance wheel, test fit the staff to the hole jewels to make sure the pivot size is correct. If the pivot turns out to be slightly large you could crack or break a jewel. Next install the replacement staff alone in the movement with the balance cock so you can check for end shake and good free spin of the staff. Be careful when tightening down the balance cock since if the staff is slightly long you can damage the new staff or cap jewel. Bring it down slowly while checking freedom of movement. After you are satisfied with the fit of the staff, then stake it to your balance wheel. I always then install the assembled staff and balance in the movement again to check again for any possible problems. Yes, you will need to poise the balance. This is done with the roller table installed, but not the hairspring. After poising I then install the hairspring and put the completed balance assembly back on the movement by itself and set the balance in motion, checking for good motion and freedom in all positions.

Poising presents a real problem. I do not own a poising table. I wonder if I can make one, using shim stock clamped between aa pair of razor blades? Hm-m-m-m. Off hand, that seems like a lot of trouble. OTOH, it is a typical machining setup problem, so not insurmountable. All one needs to know is the distance wanted between the knife edges, which is readily found, given the staff to measure from.

UPDATE: Decided to "bite the bullet" and went over to the big auction site to bid on a p[oising tool. There are bunch on there, so it shouldn't be too difficult (or expensive) to get one.

Thanks, Roger, for the advice to turn the old staff off from the back side. I would not have thought of that. The test fitting was not unexpected; that is something one typically has to do in clock work, as well. 'Course, the challenge here is that things are several orders of magnitude smaller.

@ Melvin - Do you have two you could sell me, In case I mess one up?

JAn 15 - UPDATE: Got the old staff stripped down (Finally!) Turned out I don't have the right size stump to remove the roller table, so had to pry it off with the two screwdriver method. Then, much to my chagrin, come to find out my smallest collet is 0.5, and I need a 0.3 to chuck up the balance staff to turn off the hub. SO this evening, I spent a little time making a shellac hub to fit my headstock. (I had a taper collet, and turned a taper on a piece of brass rod, then drilled a blind hole in the center, with a 0.5 mm bit. Tomorrow, I will stick the balance staff to it and turn off the hub and remove the balance wheel. Mel - I will send you an email to discuss purchasing a replacement staff. Thanks)